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使用事件侦听器在JavaScript中重新分配全局变量

event-listener variables javascript

Casey Morgan · 技术社区 · 3 周前

很抱歉,但我对JS还很陌生——我正试图使用事件侦听器分配“humanChoice”,然后在函数playRound中使用该值。然而,当我将其打印到日志中时,尽管我正在尝试分配它,但该值仍以未定义的形式返回。如有任何帮助,我们将不胜感激。谢谢

let humanChoice

rock.addEventListener('click', () => {
    humanChoice = "rock"
    playRound()
});

function playRound(humanChoice, computerChoice) {

    if (humanChoice === computerChoice) {
        console.log("It's a tie! There is no winner this round.")
    } else if (humanChoice === "rock" && computerChoice === "paper") {
        computerScore++
        console.log("You lose! Your score is " + humanScore + " and the computer's score is " + computerScore + ".")
    } else if (humanChoice === "rock" && computerChoice === "scissors") {
        humanScore++
        console.log("You win! Your score is " + humanScore + " and the computer's score is " + computerScore + ".")
    } else if (humanChoice === "paper" && computerChoice === "rock") {
        humanScore++
        console.log("You win! Your score is " + humanScore + " and the computer's score is " + computerScore + ".")
    } else if (humanChoice === "paper" && computerChoice === "scissors") {
        computerScore++
        console.log("You lose! Your score is " + humanScore + " and the computer's score is " + computerScore + ".")
    } else if (humanChoice === "scissors" && computerChoice === "paper") {
        humanScore++
        console.log("You win! Your score is " + humanScore + " and the computer's score is " + computerScore + ".")
    } else if (humanChoice === "scissors" && computerChoice === "rock") {
        computerScore++
        console.log("You lose! Your score is " + humanScore + " and the computer's score is " + computerScore + ".")
    }
}

我希望humanChoice被重新分配到“摇滚”,并允许我将其传递到playRound。但是,它返回undefined。

1 回复 | 直到 3 周前

user24924388 3 周前

看见 variable shadowing .

您在playRound中定义了一个局部变量humanChoice作为参数,但在调用它时没有传递任何值。有两种解决方案如下。
作为局部变量传递。

// let humanChoice

rock.addEventListener('click', () => {
    // humanChoice = "rock"
    playRound('rock') // pass 'rock' as parameter
});

function playRound(humanChoice) { // use local variable humanChoice
    // ...
}

或者使用全局变量

let humanChoice

rock.addEventListener('click', () => {
    humanChoice = "rock"
    playRound()
});

function playRound() { // remove local variable humanChoice
    // use global variable humanChoice
}

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